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101.
The processes of electron transfer and dissociative scattering are explored for collisions of hyperthermal NO+ on GaAs(110). The experiments reveal a marked angular dependence to O− emergence. A strong correlation between the O− scattering angle and the final atom-surface interaction site provides a map of the lateral dependence to reactivity. The results are modeled by sequential neutralization, dissociation, and electron attachment steps. Classical trajectory calculations, in conjunction with an empirical opacity function, accurately reproduce the experimental results. The opacity function is interpreted as the probability that an electron will attach to a departing O fragment as a function of the last surface site the atom impacts. The experiments indicate that O− emergence occurs predominantly for oxygen atoms which come in close contact with the localized dangling bond states of GaAs(110). 相似文献
102.
We report the results of the DC magnetization, neutron powder diffraction and neutron depolarization studies on the spin-chain
compounds Ca3Co2–x
Fe
x
O6 (x = 0, 0.1, 0.2 and 0.4). Rietveld refinement of neutron powder diffraction patterns at room temperature confirms the single-phase
formation for all the compounds in rhombohedral structure with space group Rc. Rietveld refinement also confirms that Fe was doped at the trigonal prism site, 6a (0, 0, 1/4) of Co. The high temperature
magnetic susceptibility obeys the Curie-Weiss law; the value of the paramagnetic Curie temperature (θ
p) decreases as the concentration of iron increases and it becomes negative for x = 0.4. No extra Bragg peak as well as no observable enhancement in the intensity of the fundamental (nuclear) Bragg peaks
has been observed in the neutron diffraction patterns down to 30 K. No depolarization of neutron beam has been observed down
to 3 K confirming the absence of ferro- or ferrimagnetic-like correlation.
相似文献
103.
Liwei Chen Prof. Dr. Jinkee Hong Prof. Dr. Hans-Jürgen Butt Prof. Dr. Sanghyuk Wooh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(18):4535-4542
Metal oxide photocatalysts (MOPCs) decompose organic molecules under illumination. However, the application of MOPCs in industry and research is currently limited by their intrinsic hydrophilicity because MOPCs can be wetted by most liquids. To achieve liquid repellency, the surface needs to possess a low surface energy, but most organic molecules with low surface energy are degraded by photocatalytic activity. Herein, current methods to achieve liquid repellency on MOPCs, while preventing degradation of hydrophobic coatings, are reviewed. Classically, composite materials containing MOPCs and hydrophobic organic compounds possess good liquid repellency. However, composites normally form irregular coatings and are hard to prepare on surfaces such as those that are mesoporous or nanostructured. In addition, the adhesion of composites to substrates is often weak, resulting in delamination. Recent studies have shown that the direct grafting reaction of polydimethylsiloxane (PDMS) from silicone oil (methyl-terminated PDMS) under illumination results in a stable polymer brush. This easy and simple grafting method allows us to create stable liquid-repellent surfaces on MOPCs of various types, structures, and sizes. In particular, super-liquid-repellent drops with an underlying air layer can be created on PDMS-grafted nano-/microstructured MOPCs. Potential applications of surfaces combining liquid repellency and photocatalytic activity are also discussed; thus offering new ways of using MOPCs in a wider range of applications. 相似文献
104.
A series of NiMnTi mixed metal oxides (Ni/Mn-TiO2, Mn/NiTi-LDO and TiO2/NiMn-LDO, NiMnTi-LDO) were synthesized via different assembling methods and evaluated in the selective catalytic reduction of NOx with NH3(NH3-SCR). As the results presented, catalysts via diverse assembling methods of LDHs templates afforded different catalytic denitrification (DeNOx) performance, which might be related to the exposure degree of active constituents and the interaction intensity between metal components. Noticeably, compared with Ni/Mn-TiO2, Mn/NiTi-LDO and TiO2/NiMn-LDO catalysts, the NiMnTi-LDO catalyst deriving from one step in-situ method NiMnTi-LDH precursor template exhibited the most desirable performance at temperature window of 150–360 °C in NH3-SCR (above 90% NOx conversion with 95% N2 selectivity). The specific structure and property of samples were correlated by means of a series of characterizations, where the results indicated that NiMnTi-LDO possessed the highest surface area, the strongest redox ability, the most abundant acid amount and the best dispersion. 相似文献
105.
Jing Zhao Prof. Jingjun Liu Chun Jin Nan Wang Prof. Feng Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(55):12606-12614
The construction of nano-scale hybrid materials with a smart interfacial structure, established by using rare earth oxides and carbon as building blocks, is essential for the development of economical and efficient catalysts for oxygen reduction reactions (ORRs). In this work, hexagonal La2O3 nanocrystals on a nitrogen-doped porous carbon (NPC) derived from crop radish, served as building bricks, are prepared by chemical precipitation and then calcination at elevated temperatures. The obtained La2O3/NPC hybrid exhibits a very high ORR activity with a half-wave potential of 0.90 V, exceeding that of commercial Pt/C (0.83 V). Both DFT theoretical and experimental results have verified that the significantly enhanced catalytic performance is ascribed to the formation of the C−O−La covalent bonds between carbon and La2O3. Through the covalent bonds, electrons can transfer from the carbon to La2O3 and occupy the unfilled eg orbital of the La2O3 phase. This results in the accelerated adsorption of active oxygen and the facilitated desorption of the surface hydroxides (OHad−), thereby promoting the ORR over the catalyst. 相似文献
106.
Marisa C. Oliveira Renan A. P. Ribeiro Elson Longo Mauricio R. D. Bomio Sergio R. de Lázaro 《International journal of quantum chemistry》2020,120(22):e26368
The structural, electronic, and vibrational properties of two leading representatives of the Zn-based spinel oxides class, normal ZnX2O4 (X = Al, Ga, In) and inverse Zn2MO4 (M = Si, Ge, Sn) crystals, were investigated. In particular, density functional theory (DFT) was combined with different exchange-correlation functionals: B3LYP, HSE06, PBE0, and PBESol. Our calculations showed good agreement with the available experimental data, showing a mean percentage error close to 3% for structural parameters. For the electronic structure, the obtained HSE06 band-gap values overcome previous theoretical results, exhibiting a mean percentage error smaller than 10.0%. In particular, the vibrational properties identify the significant differences between normal and inverse spinel configurations, offering compelling evidence of a structure-property relationship for the investigated materials. Therefore, the combined results confirm that the range-separated HSE06 hybrid functional performs the best in spinel oxides. Despite some points that cannot be directly compared to experimental results, we expect that future experimental work can confirm our predictions, thus opening a new avenue for understanding the structural, electronic, and vibrational properties in spinel oxides. 相似文献
107.
We optimized photocatalytic hydrogen production over TiO2-based photocatalyst by varying the dopant (nickel and copper oxide), thin film active area, nature and concentration of sacrificial agents, and light intensity in a photoelectrochemical (PEC) cell/dye-sensitized solar cell (DSSC). Various characterization techniques have been used to investigate the structural, morphological, optical, and PEC behavior of single and codoped TiO2. The TiO2 decorated with both Cu and Ni oxides with active area of 1 cm2 in a mixture of 5 vol % glycerol and 1 M KOH under light intensity of 100 mWcm?2 produced the maximum hydrogen of 338.4 μmol cm?2 for 2 h. The superior photocatalyst performance of this photocatalyst is attributed to its small crystallite size and large pore size, as confirmed by X-ray diffractometer, Transmission electron microscopy (TEM), and surface area of Brunauer-Emmet-Teller (SBET). The absorption edges of this photocatalyst had the highest red shift compared with single doped and pure TiO2 because of more indirect transitions of the photoexcited electrons, greater charge carrier separation, and lower recombination rate. The photoanode active area of 1 cm2 with better photocatalytic performance correlated with the number of defects and grain boundaries. Glycerol shifted the conduction band of the photocatalyst to more negative flat potential compared with others. Increasing the concentration of glycerol further than 5 vol% saturated the photocatalyst active sites, increased photooxidation intermediates of glycerol, and reduced the hydrogen production. The light intensity had the maximum impact on the hydrogen production and could strongly control the number of charge carriers in both the PEC cell and the DSSC. 相似文献
108.
BaTiO3–Bi0.5Na0.5TiO3 is one of the promising candidates as a high-temperature relaxor with a high Curie temperature and several preferred dielectric characteristics. It has been found experimentally for a long time that adding calcium to BaTiO3–Bi0.5Na0.5TiO3 improves its temperature characteristic of the capacitance [J. Electron. Mater. 39, 2471]. In this study, Calcium (Ca) defects in perovskite BaTiO3 and Bi0.5Na0.5TiO3 have been studied based on first-principles calculations. In both BaTiO3 and Bi0.5Na0.5TiO3, our calculations showed that Ca atom energetically prefers to substitute for the cations, that is Ba, Bi, Na and Ti, depending on the growth conditions. In most cases, Ca predominantly substitutes on the A-site without providing additional electrical carriers (serve as either neutral defects or self-compensating defects). The growth conditions where Ca can be forced to substitute for B-site (with limited amount) and the conditions where Ca can be forced to serve as an acceptor are identified. Details of the local structures, formation energies and electronic properties of these Ca defects are reported. 相似文献
109.
化学发光法是测量低浓度的大气氮氧化物含量的有效方法,可用于24h连续自动分析的大气环境监测系统。然而该方法需要高温转换室、高压臭氧发生模块、高温反应室等模块,使得仪器内的环境分布极为复杂,仪器在长时间运行后容易出现灵敏度下降、信噪比降低等现象。针对上述现象,设计了用于仪器的光信号探测模块的温度控制系统。该温控系统基于PID控制原理,通过AVR单片机ATMEGAl6对半导体制冷片(Ther—mo—ElectricCooling,TEC)的闭环控制来实现温度的精密控制。实验结果表明,该系统可以使光信号探测模块的温度控制在5℃±0.1℃,光电倍增管的暗噪声从25℃时的363个/s下降到5℃时的8个/s光子数,噪声波动标准差也从22降到3,能够很好地满足系统对信号探测稳定性的要求。 相似文献
110.
G. R. Kosmambetova V. I. Gritsenko P. E. Strizhak A. M. Korduban 《Theoretical and Experimental Chemistry》2006,42(2):133-138
We have studied the catalytic properties of copper-cerium oxide catalysts, supported on zirconium, aluminum, titanium, and
manganese oxides, in the reaction of selective oxidation of CO in hydrogen-rich mixtures. We have shown that the high activity
and selectivity of catalysts supported on zirconium and aluminum oxides is connected with the presence of (in addition to
divalent copper) higher amounts of copper in the (+1) oxidation state in the catalysts.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 119–124, March–April, 2006. 相似文献